1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device provided with a flexible printed circuit (FPC) on a main support, the FPC integrally formed with a color sensor to detect colors of red, green and blue (RGB).
2. Description of the Background Art
Generally, an LCD device comprises an LC panel including a thin film transistor (TFT) array substrate, a color filer substrate facing the TFT array substrate, and an LC layer injected between the two substrates; a driving unit for displaying images on the LC panel; and a backlight unit for supplying light to the LC panel.
On the TFT array substrate, unit pixels are arranged in the form of matrixes. The unit pixels are defined as a plurality of data lines arranged on the TFT array substrate in a vertical direction with a constant gap therebetween are formed to cross a plurality of gate lines arranged in a horizontal direction with a constant gap therebetween.
On the color filter substrate, formed are RGB sub-color filter layers in correspondence to the pixels of the TFT array substrate. On the color filter substrate, further formed is a black matrix for preventing light from leaking between the color filter layers, and for preventing color interference of light passing through the pixels.
Common electrodes and pixel electrodes are respectively formed on each surface of the color filter substrate and the TFT array substrate facing each other, thereby applying an electric field to the LC layer. Here, the pixel electrodes are formed on the TFT array substrate according to each pixel, whereas the common electrodes are integrally formed on an entire surface of the color filter substrate.
A voltage applied to the pixel electrode is controlled under a state that a voltage is applied to the common electrode, thereby changing an oriented status of LC molecules on the LC layer. Accordingly, optical transmittance of the pixels is individually controlled.
The backlight unit serves to supply light to the LC panel that does not spontaneously emit light. An optical transmittance is determined according to an oriented status of LC molecules when light supplied from the backlight unit passes through the LC layer, thereby displaying images.
The backlight unit is largely classified into an edge type and a direct type according to a position of a lamp used as a light source. According to the edge type backlight unit, a lamp is disposed at one side or both sides of an LC panel, and light emitted from the lamp is guided by a light guide plate thus to be displayed on an entire part of a screen of the LC panel.
According to the direct type backlight unit that has developed since the LC panel becomes large with a size more than 20-inch, a plurality of fluorescent lamps are arranged in serial at a lower surface of a diffusion plate, and light is directly irradiated onto an entire surface of the LC panel. The direct type backlight unit implements higher optical efficiency than the edge type backlight unit, thereby being mainly used at an LCD device having a large screen requiring high brightness.
The light source includes a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), an Electro Luminesence (EL), a Light Emitting Diode (LED), etc. Here, the CCFL and the LED are mainly used due to low power consumption.
The fluorescent lamp has advantages that a relatively higher brightness and uniform brightness are implemented. However, the fluorescent lamp has a disadvantage that a color reproduction ratio is low.
The LED or EL has advantages that brightness can be partially controlled, and a color reproduction ratio is high. However, the LED or EL has disadvantages that a relatively lower brightness is implemented, and bright uniformity is lowered.
FIG. 1A is a planar view showing a backlight unit in accordance with the conventional art, and FIG. 1B is a sectional view of a liquid crystal display (LCD) device having the backlight unit of FIG. 1A.
Referring to FIGS. 1A and 1B, the conventional LCD device comprises a first light emitting portion 10 having a spontaneous light emitting lamp 11a, and generating light of R, G and B; a second light emitting portion 20 having a bar-shaped plurality of fluorescent lamps 21 arranged in parallel; a color sensor 50 for sensing a wavelength of light emitted from the first light emitting portion 10, and outputting as a voltage value; a driving circuit portion 30 for controlling a color temperature of the spontaneous light emitting portion 11a of the first light emitting portion 10 according to the voltage value output from the color sensor 50; and an interface 35 for transmitting a signal received from outside to the driving circuit portion 30.
The second light emitting portion 20 consists of fluorescent lamps 21 that generate white light. As the fluorescent lamp 21, a Cold Cathode Fluorescent Lamp (CCFL), or a Hot Cathode Fluorescent Lamp (HCFL), etc. may be used.
More specifically, as shown in FIG. 1B, the fluorescent lamps 21 of the second light emitting portion 20 are formed below an LC panel 60, and the first light emitting portion 10 is formed at a side surface of the LC panel 60. A light guide plate 40 for guiding light emitted from the first light emitting portion 10 to the LC panel 60 is further installed below the LC panel 60.
The color sensor 50 for sensing a wavelength of light emitted from the first light emitting portion 10 is installed on an upper end of the light guide plate 40.
A reflection plate (not shown) for guiding light emitted from the second light emitting portion 20 to the LC panel 60 to the maximum may be further installed on an inner surface of a lower cover 1 of the LCD device.
However, when the color sensor is installed on an upper end of the light guide plate, the color sensor may be moved by an external force thus to have a position transition. This may cause a mal-operation of color control and color calibration.
Furthermore, processes to install the color sensor on an upper end of the light guide plate, and processes to electrically connect the color sensor to the circuit driving portion are complicated and difficult, which may require additional costs.